A test for comparing the means of two samples, or the mean of one sample (or even parameter estimates) with a specified value; also known as the "Student t-test" after the pseudonym of its inventor.

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Interpreting results of Libreoffice Calc's TTEST function [duplicate]

I'm doing some data analysis on a small dataset (35 individuals) and I'm wondering whether my findings are statistically significant. Individuals are asked questions before and after a treatment, so ...
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16 views

Bootstrapping and comparing mean distributions

Is the following a reasonable approach to assess the statistical significance of the difference between two groups' For each group 1) Subsample with replacement 2) Take the mean of the subsample 3) ...
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1answer
12 views

Two-way ANOVA doesn't detect differences between conditions in a specific group?

OK, so let's say we have independent variables Condition (A or B) and Race (1 or 2 or 3). Then say we have a dependent variable X. We can run a two-way ANOVA to find out if there's an effect due to ...
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23 views

Bootstrapping a t statistic - Rationale and procedure

I was hoping someone could help me out with this. I've seen similar questions on the forum, but I need to know if I've understood the correct rationale and procedure for bootstrapping for my ...
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1answer
28 views

Why do we ignore the main effects when the interactions are not significant in a three-way ANOVA?

I'm following an SPSS guide online, and the procedure is to first test for a three-way interaction. In my case there was no sig. three-way interaction. Then the procedure asks me to consider two-way ...
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26 views

Testing Clustering Variables

I have two clusters. Those two clusters were obtained using Fuzzy C-Means with 8 variables. I'd like to know which variables have important role in differentiating the two clusters. Can I use t test ...
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1answer
39 views

Is it appropriate to use t-tests to find the most different outcomes?

I have a large CSV file of spending by individuals on different drugs. I want to find the drugs with the most different spending patterns by gender. The file looks a bit like this, but with 7.5k ...
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45 views

T tests on proportions - Wrong, but how wrong?

In psychology, and probably a number of other disciplines, it's common practice to test between-groups effects on a binary variable, such as accuracy, by aggregating data within participants, and then ...
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57 views

How to analyze data once broken down into gender, race, etc

I have two conditions, Treatment A, and Treatment B. Participants are randomly assigned to a treatment at the outset. Then I run unpaired t-tests on the data to find any differences. BUT I am also ...
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120 views

Logistic regression or T test?

A group of persons answers one question. The answer can be "yes" or "no". The researcher wants to know whether age is associated with the type of answer. The association was assessed by doing a ...
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20 views

Using regression fit to compare two groups at a time point

I have estimated a regression model in R with two groups, included as factors. Their regression fits are visually quite different, but I would like to statistically test if they are different on a ...
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21 views

what does value of t test mean? [duplicate]

I have two distribution of one variable and I've used t test to find how much they are significantly different. But I'm not very familiar with this test and don't know what does this values mean? is ...
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1answer
49 views

1 and 2 sample t-tests for plants and soils question!

I have a good friend who has an experiment where he grows different kind of plants on various soils and measures the protein content and weight each week for 5 weeks. His goal is to determine which ...
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15 views

How do I calculate a t-score from a p-value (gain scores and N also available)

I have this problem that only the gain scores with the p-value of a t-test are given in a scientific article. The authors neglected to report the t-test statistic and I'm stuck on figuring out how to ...
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2answers
31 views

Can a linear relationship between estimated standard deviations and estimated means be used to increase the power of a t-test?

Let’s say I have a high number of treatments (40) but a low number of replications per treatment (n=4), and I am interested in comparing values between two particular treatments (let’s say treatments ...
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11 views

Mixed ANOVA interaction effect - How do I which treatment was more effective?

I have conducted a mixed between-within ANOVA with 3 intervention groups and 2 measurement times (pre/post) in SPSS. There was a significant Time*Group interaction, but significant main effects. How ...
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18 views

What is equivalent of pairwise t-test for categorical variables?

I am doing some analysis where I have two monthly snapshot data (containing both numeric and categorical variable). Now I am trying to see which variable changed significantly from the first month in ...
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28 views

Choosing the correct experimental design

So lets just say I conducted a chi-squared contingency analysis test (I did btw) on 40 separate fish. Each individual fish only went through one treatment trial, where they were subjected to ...
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11 views

Multiple Comparisons for paired control and treatment groups

I want to conduct a post-hoc analysis on the impact of a treatment compared to the control Each control and treatment were selected to that the underline features are similar. For e.g. in the ...
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16 views

Significance of excess return using geometric mean

Since I am writting an assignement about a contrarian-strategy I have to test if the excess returns are significant or not. I calculated the excess returns this way: geomean(pf_returns) - ...
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3answers
47 views

Is ANOVA the same as running 3 t-tests?

I have a group of subjects which did tests under 3 different conditions. If I now want to compare variables with a ANOVA, is it right that I get the same p-values as if I would run 3 t-tests ...
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1answer
22 views

Does the bonferonni correction change the outcome of the p-value or is it just changin what you accept as significant?

For some reason I can't seem to integrate the bonferonni corrected p adjustment into my multiple comparisons t test in r so I need to do each of my 3 tests individually. What I wondered was do I need ...
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9 views

ttest in sas with proc ttest

I have a data with GENDER=(1/0) INCOME SENIORITY=(1/0). I need to run a ttest on INCOME by GENDER for SENIORITY=1. As far as I know, the default of HO=0, which means that there is no difference ...
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1answer
26 views

Testing for three means in order

Say I have data as follows: type|value where type takes values $A$, $B$ and $C$ and value is ...
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Paired data measured over different timeframe analysis

For number of patients I have two measurements of the same characteristic. For example: patient 1: one measured value at date1 and second measured value at date2 patient 2: one measured value at ...
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48 views

Testing for Significance - Should t-test be used or paired t-test

Let's say there are 100 stock exchanges on which I trade stocks and the cost of me trading has the averages below ...
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1answer
37 views

Similarity between two small datasets

I have gone through several test's (Kolmogorov-Smirnov, t-test, u-test etc..) but I am not sure which one to use when it comes to comparing two small data sets, lets say of size 10 each. ...
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6 views

Which test to do for comparison effect context over time

I'm currently working on my dissertation, and have finally gotten to the point to where I can conduct the analyses for my hypotheses. My main hypothesis is: 'Study organizations have a positive ...
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16 views

Which test for paired data with small sample size?

I have four paired samples (subjects tested once, then again under different conditions), and am unsure which test to use to calculate significance with such a small sample size. It was suggested to ...
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1answer
36 views

Should I bother that t-test power is relatively small when H0 is already rejected?

I have two quite small samples ($n=7$ for each) and I get two-sample t-test power for them 0.49, which is relatively small (calculated by R power.t.test()). ...
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1answer
32 views

Comparing ratio response data with a t-test

I am interested in knowing if the ratio of organisms between two dates differs between control and experimental plots. For each plot, I measure the number of organisms on day one and day thirty. I ...
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52 views

paired t-test… for proportions?

I did a pre-education and post-education quiz for a group of anonymous individuals. Individuals took a 2-3 question quiz, viewed an educational video, and then took another 2-3 question quiz. The quiz ...
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19 views

Do I need to adjust the sample distribution to test significance?

The question in the title is probably not very clear, so let me explain better what my problem is. Suppose I have the following data from a survey: A categorical variable indicating the age of the ...
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1answer
56 views

what is difference between t-test and 10-fold validation?

one of famous significant test is t-test which can conclude is our result by chance or not using previous results and their variance. Also when we use 10-fold validation we break our dataset to train ...
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3answers
69 views

How to find the right test?

I have a problem in medicine: Each patient can have several (3) symptoms (A,B,C) of a disease at the same time. For each symptomtype we can measure a score i.e. A=0.2, B=0.45, C=0.8. The aim is that ...
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1answer
83 views

How to compare stochastic algorithms, before and after modification

I would appreciate suggestions on how I could make some specific statistical claims about the efficacy of changes to an algorithm. My statistics background is pretty minimal (I'm working on it). I ...
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1answer
40 views

which statistical t-test to use when having data from different demographies?

I would like to know whether Blood Pressure is significant in contributing to a diseaseHypo. I have data from three different ...
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1answer
54 views

Paired two one-sided t-tests (TOST) with unequal sample sizes

I have data from two populations (let's call them "before" and "after"), collected in a paired fashion. That is, I take a measurement under one set of conditions before, and then I can take multiple ...
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18 views

Testing if means are different and reporting on that usng R t.test

Lets say I have the 4 means that are the average response time for some variable: Response Time A .12 B .16 C .65 D -.35 I want to test ...
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0answers
19 views

t-Test Statistic Distribution [duplicate]

If I am testing for means and I perform a t-test but my data is only approximately normally distributed is then my test statistic exactly t distributed or also approximately t-distributed?
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4 views

statistical analysis of intervention bases research

I'm doing a study and asking the research question, does teacher immediacy behaviours improve cognitive learning in ESL students? I am training teachers in immediacy behaviours, then seeing if this ...
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35 views

Basic hypothesis testing question

This is (I think) a fairly basic question but my stats are quite rusty. It's akin to the "is the coin fair" question, but a little more involved. Suppose I have a wagering algorithm, and I am trying ...
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1answer
44 views

Should I use the mean difference or mean ratio for a t-test?

I have a quantitative variable (medication dose) that is paired: dose of medication before surgery and after surgery for 76 patients. I was under the impression that I should calculate the mean of ...
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12 views

Ttests for DNA sequences

Let's say I have two sets(1000 sequences in each set: set1 and set2) of independent DNA sequences of length 30. I created a HMM model by using DNA sequences in set1 which calculate Prob(Seq/Model). It ...
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1answer
18 views

Comparing three groups for one variable when two of the groups' values are zero

I'm trying to compare three groups but the fact that two of theml only show values of zero is giving me a hard time. Specifically, I'm comparing the production of a metabolite (M3G) by three cell ...
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1answer
40 views

How can I test possible reasons for the relationship between income and handedness?

For a project, I am trying to determine what accounts for the difference in income between left handed people and right handed people. (For example, whether it is only among males, or only in a ...
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2answers
79 views

Which standard deviation to use for p-value of regression coefficients?

Matlab generates regression coefficients for vector time series models ("vgxvarx"). For a given regression coefficient, the p-value is just the area under the t-distribution beyond |t| > ...
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53 views

What statistical test should I use between two scenarios?

Scenario: I have a test data of response time of two websites in two different servers. Let's say website A and website B are tested on server A and server B not respectively but website A and website ...
2
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0answers
44 views

MANOVA as protection against Type I errors

OK, so I have absolutely scoured the internet, and it appears that there is consensus (among people who really care about Type I error) that doing a MANOVA before doing multiple ANOVAs does nothing to ...
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1answer
44 views

Why exactly is normality an assumption in a T-test but not a Wilcox rank sum/Mann Whitney U test when obtaining a p-value?

In addition to the question, please do correct anything below that I have incorrect. I understand how the test statistics for a t-test and WRS/MWU test are calculated. In a t-test, $t=\frac{\bar ...